Police arrested a videographer in a wheelchair in Ferguson, Missouri, on Monday night during a small demonstration to mark six months since an officer shot and killed unarmed 18-year-old Michael Brown.

Heather De Mian, who has live-streamed the months of protests after Brown’s death, was among seven people detained by officers outside the Ferguson police department, according to observers.

Several photographs taken outside the department and posted to Twitter showed De Mian on the ground beside her wheelchair.

Earlier in the evening De Mian had been broadcasting via UStream live from Canfield Drive, the residential side-street about two miles from the police department where Brown was shot by officer Darren Wilson following an altercation on 9 August.

People gathered at the station in support of De Mian, who was later released and gave her version of events.

It was not immediately clear what De Mian, who is better known to Ferguson activists by the screenname @MissJupiter1957, was accused of doing wrong. De Mian has Ehlers-Danlos syndrome, a disorder of the body’s connective tissue.

Onlookers said some protesters were arrested for doing graffiti in chalk. Slogans about Wilson and tributes to Brown were photographed on a wall outside the police headquarters. Neither Ferguson’s police chief Thomas Jackson nor a spokesman for the department responded to a request for comment late on Monday.

Successive nights of clashes between officers in riot gear and protesters took place outside the police headquarters in November when a grand jury decided not to indict Wilson. The US Department of Justice has been conducting an inquiry into whether federal civil rights charges should be brought against Wilson. No charges are expected.

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